【英文兒童科普】---98、​物理變化和化學變化:孩子們的化學課堂

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物理變化和化學變化：孩子們的化學課堂

Physical and Chemical Changes

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你現在收看的是《基礎校園》

You’re watching FreeSchool!

無論你在哪兒 無論你在做什麼

No matter where you are, or what you are doing,

你周圍的事物一直在變化著

things are changing all around you.

無論是植物的生長 還是木柴的燃燒

Whether it’s plants growing or logs burning,

甚至當你在吃東西的時候

or even if you’re just eating food,

你周圍的東西

the materials around you

大小 形狀 結構都在發生改變

are changing in size, shape, and structure;

釋放或是吸收能量

releasing or absorbing energy,

並且生成新的物質

and creating new substances.

在化學上 大部分變化被分成兩類：

In chemistry, most changes are divided intotwo categories:

物理變化和化學變化

physical changes and chemical changes

物理變化會

A physical change is something that

改變物體或是物質的物理性質

changes the physical properties of an object or substance

如大小 形狀 或是組成

– like size, shape, or form.

剪下一塊布就是一個物理變化

Cutting a piece of cloth is an example of a physical change.

雖然剪布的時候改變了它的形狀和大小

Even though the cloth changes shape and size when it is cut,

但沒有產生新的物質

it does not create a new substance.

它仍然是塊布

It’s still cloth!

即使布都被縫起來了

Even if the pieces of cloth are sewn together

並且做成了襯衫

and made into a shirt,

仍然只有物理變化發生

only physical changes have occurred.

這件襯衫還是用同樣的物質做成的

The shirt is still made of the same substance

仍是最初的那塊布 只是變成了新的形式

as the original cloth, just in a new form.

另一種物理變化包括物質狀態的改變

Another type of physical change involves changing states of matter,

水就是其中一個很好的例子

and water is a great example of this.

冰融化變成了水

Ice melts and becomes water,

水蒸發變成了水蒸氣 但不論是哪種形式

and water evaporates to become steam, but no matter its form,

水仍然是水

the water is still water.

辨別出物理變化的一種方式

One way we can tell this is a physical change is

就是這些變化可以被撤銷

that the change can be undone.

水蒸氣能凝結變回液體狀的水

Water vapor can condense back into liquid water,

液體狀的水可以凍結變回冰

and liquid water can be frozen back

它並沒有變成其他物質

into ice without changing to a different substance.

事實上 許多物理變化都能撤銷

In fact, many physical changes can be undone.

舉個例子 我們知道糖溶解於水中

For example, we know that dissolving sugar

是一個物理變化

into water is a physical change

因為即使糖和水被混合在了一起

because even though the sugar and the water are mixed together,

但它們沒有結合在一起 生成一種新的物質

they do not combine and create a new substance.

它們仍然是糖和水

They are still just sugar and water,

並且它們可以被分開

and they can be separated from each other.

不是所有混合物都像糖和水一樣可以被輕易分開

Not all mixtures are as simple to separate as sugar and water.

當你將黃油 糖 麵粉和雞蛋混合在一起

When you mix butter, sugar, flour, and eggs,

就沒有一個實用的辦法將它們再次分開

there is not a practical way to separate them again,

但是這仍然是一個物理變化

but it is still only a physical change.

將混合物放進烤箱加熱時

The chemical change occurs when you put your mixture

化學變化就發生了

in the oven and add heat.

烘烤有許多化學變化的標誌

Baking has many of the indications of a chemical change.

在烤箱中的混合物吸收了熱量

The mixture in the oven absorbs heat.

它改變了顏色並且產生了一種氣味

It also changes color and produces an odor.

氣體被釋放 使得被烘烤的東西膨脹

Gases are released, which is what helps the baked goods to rise.

最終這種變化被無法撤銷

Finally, this change can not be undone –

你不能使蛋糕變回它烘烤前的樣子

you can’t unbake a cake.

化學變化發生時 兩種或兩種以上物質微粒

Chemical changes occur when the particles of two or more substances

重新排列形成一種新的物質

are rearranged to form a new substance.

例如 當你燃燒木頭時

For example, when you burn wood,

木頭變成了一種新的物質——灰燼

the wood is transformed into a new substance – ash.

就像烘烤一樣 這種變化不能被撤銷

Just like in baking, this change cannot beundone.

木頭像曲奇一樣改變了顏色

Also like the cookies, the wood changes color,

釋放了氣體——煙——產生了氣味

releases gases – smoke – and produces an odor.

和烘烤不一樣的是

Unlike in baking,

這種化學變化釋放了熱量和光

this chemical change releases heat and gives off light.

化學變化就發生在我們的身邊

Chemical changes take place all around us.

如金屬的生鏽 煙火的燃放 水果的成熟

Metal rusting, fireworks exploding, fruit ripening,

以及食物的消化 都是化學變化

and digesting food are all examples of chemical changes!

如果你不確定某個變化是化學變化還是物理變化

Here are some clues to look at if you’re not sure

下面一些線索可以幫助你

whether something is a chemical or physical change.

化學變化總是生成一種新的物質

Chemical changes always form a new substance.

它們能夠吸收或釋放熱量

They may absorb or release heat.

有時化學變化會改變顏色

Sometimes a chemical change will cause a change in color,

產生氣味和聲音

produce an odor, create a sound,

釋放氣體 或者產生光

release gases, or produce light.

化學變化通常不能被撤銷

Chemical changes usually cannot be undone.

物理變化不能形成新的物質

Physical changes do not form a new substance.

物理變化可以改變物體的形狀或大小

A physical change may change the shape or size of an object.

它可能改變物質的狀態

It may change the state of a substance’s matter.

許多物理變化能在某些條件下被撤銷

Many physical changes can be undone in some way.

在物理變化中

In a physical change,

你關注的從始至終都是同一種的物質

you end up with the same substance you started with,

即使外表看起來不同

even if it looks different.

希望你能享受今天學習物理和化學變化的過程

I hope you enjoyed learning about physicaland chemical changes today.

看看周圍

Look around and see

你是否能鑑別出周圍的物理變化和化學變化

if you can identify the physical and chemical changes around you!

下次再見

Goodbye till next time!

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